Musannaf Ibn Abi Shayba 28:21

Waki’ narrated to us, he said: Sufyan narrated to us, from Harun al-Hadrami, from Abu Bakr ibn Hafs, that ‘Umar ibn al-Khattab appointed a man [to a position]. The man said, "O Commander of the Faithful, keep my secret." He said, "Sit down and keep my secret."